1. Field of the Invention
This invention relates to an improved method for making fiber-reinforced articles and to improved articles made thereby. More particularly, the invention relates to an improved method for making a thermoplastic article having a fiber-reinforced structure.
2. Description of the Prior Art
Reinforced thermoset plastics and composite materials such as, for example, fiberglass reinforced polyesters, and a variety of methods for making the same are known in the art. Many of these known articles and methods are described in the "SPI HANDBOOK OF TECHNOLOGY AND ENGINEERING OF REINFORCED PLASTICS/COMPOSITES," 2d ed., J. Gilbert Mohr, Senior Author, Van Nostrand Rheinold Company, New York, 1973, including hand lay-up methods, pp. 15-54; spray-up methods, pp. 77-94; cold press (or cold-forming) molding, pp. 352-358; the Marco method, pp. 103 et seq.; preform and SMC molding, pp. 86-87, 109-111, 127-143, and 175-239; and vacuum bag molding, including pressure bag molding and rubber plunger molding modifications thereof, pp. 77-94. Articles prepared by these methods include laminates or composites. As used throughout the specification, the term "laminate" means an article containing one or more of a single type of reinforcement material and a surface of a cured resin mixture; the term "composite" means an article containing a mixture of layers of different types of reinforcement material and a surface of cured resin mixture. U.S. Pat. Nos. 3,915,783 and 3,567,568 and 3,867,221 and British Pat. Nos. 1,432,333 and 1,068,503 disclose laminates and composites and methods for preparing the same. These known methods suffer one or more of the disadvantages including poor control of resin application and distribution, poor control of compaction; poor control of fumes from the resin; relatively high labor costs, relatively slow production cycle; relatively expensive tooling and equipment; high maintenance costs; and difficulty in obtaining an optional combination of physical properties, cosmetic surface appearance, and design characteristics. There yet exists a need in the art for articles, and methods for preparing the same, possessing an optimal combination of two opposing physical properties--high strength of the reinforcing material and low stiffness modulus of the plastic phase.